A Prospective Observational Study on Risk Factors of Developing and Prevalence of Trephined Syndrome in Patients After Hemispheric Decompressive Craniectomy and Effect of Cranioplasty on Functional and Cognitive Recovery

Decompressive craniectomy is a neurosurgical procedure that is used frequently for mass and/or intracranial hypertension. The Trephined Syndrome (or Sinking Skin Flap Syndrome) is a neurological deterioration which follows craniectomy and which is attributed to a large bone flap size. The symptomatology is varied but includes headache, aggravation of a hemisyndrome or cognitive disorders, often has an orthostatic component and improves or disappears with cranioplasty.

The pathophysiology of the Trephined Syndrome is not clearly understood. The hypothesis is that the contents of the skull, which is no longer isolated by the bone, is then subjected to atmospheric pressure, which would lead to changes in the blood flow, but also abnormalities in the circulation of the cerebrospinal fluid and even cell metabolism.

The precise incidence of the Trephined Syndrome is poorly known but is described to be 7% up to 26%. It is much likely underestimated since it concerns patients with preexisting neurological symptoms and often multiple comorbidities. Furthermore its presentation varies in a way, that in certain patients the Trephined Syndrome manifests itself by neurological aggravation, while in other patients it is only the absence of evolution in rehabilitation, followed then by improvement after cranioplasty, which makes it possible to retain this diagnosis a posteriori.

The diagnosis is also difficult since it is a clinical diagnosis of exclusion. The cerebral imaging that shows contralateral herniation than the craniectomy is pathognomonic, but is not a gold standard for diagnosis, since the symptomatology can occur before this stage of radiological presentation.

It is, of course, necessary to wait until the regression of the edema makes it possible to restore the flap without risk of inducing a new lesion but the ideal moment of the cranioplasty is unknown. The risk of infectious disease may be increased during "early" remission, on the other hand the risk of developing the Trephined Syndrome or other complications increases during "late" cranioplasty.